Background Australia has experienced extreme fire weather in recent years. Information on the impact of fine particulate matter (PM_2.5) from landscape fires (LFs) on cardiorespiratory hospital admissions is limited.

Methods We conducted a population-based time series study to assess associations between modelled daily elevated PM_2.5 at a 1.5×1.5 km resolution using a modified empirical PM_2.5 exposure model during LFs and hospital admissions for all-cause and cause-specific respiratory and cardiovascular diseases for the study period (2015–2017) in Perth, Western Australia. Multivariate Poisson regressions were used to estimate cumulative risk ratios (RR) with lag effects of 0–3 days, adjusted for sociodemographic factors, weather and time.

Results All-cause hospital admissions and overall cardiovascular admissions increased significantly across each elevated PM_2.5 concentration on most lag days, with the strongest associations of 3% and 7%, respectively, at the high level of ≥12.60 µg/m³ on lag 1 day. For asthma hospitalisation, there was an excess relative risk of up to 16% (RR 1.16, 95% CI 1.00 to 1.35) with same-day exposure for all people, up to 93% on a lag of 1 day in children and up to 52% on a lag of 3 days in low sociodemographic groups. We also observed an increase of up to 12% (RR 1.12, 95% CI 1.02 to 1.24) for arrhythmias on the same exposure day and with over 154% extra risks for angina and 12% for heart failure in disadvantaged groups.

Conclusions Exposure to elevated PM_2.5 concentrations during LFs was associated with increased risks of all-cause hospital admissions, total cardiovascular conditions, asthma and arrhythmias.